In the International Telecommunication Union Radio communication sector (ITU-R), a standardization work for International Mobile Telecommunication (IMT)-Advanced (i.e., the next-generation mobile communication system after the third generation) is in progress. IMT-Advanced sets its goal to support Internet Protocol (IP)-based multimedia service at the data transfer rate of 1 Gbps in stop and slow-speed moving states and of 100 Mbps in a fast-speed moving state.
3GPP (3rd Generation Partnership Project) is a system standard which fulfills the requirements of IMT-Advanced, and it prepares improved LTE-Advanced (LTE-A) of LTE (Long Term Evolution) based on OFDMA (Orthogonal Frequency Division Multiple Access)/SC-FDMA (Single Carrier-Frequency Division Multiple Access) transmission schemes. The LTE-A is one of the strong candidates for IMT-Advanced. Relay node technology is included in the major technologies of the LTE-A.
A relay node (RN) is an apparatus for relaying signals between a base station and a user equipment (UE) and used to extend the cell coverage of a wireless communication system and improve the throughput.
A RN operating in the relaying mode (i.e., RN receives downlink backhaul signal from its base station in the backhaul subframes and forwards the relevant data to the associated relay UEs in the access subframes) sometimes suffers from the backhaul link failure due to some reasons such as the clock drift, channel information feedback error, or relocation of RN. If this link failure occurs in the backhaul link, the RN is not able to receive control channels and data channels, which implies that that RN cannot receive data to be forwarded to UEs anymore.
There is a need how to recover the above-mentioned backhaul link failure by the RN.